The kinetic and structural properties of acid phosphatase isoenzymes will be examined. An interconversion of isoenzymes (or enzyme forms) of possible clinical significance will be examined, and the structural characteristics of the enzyme forms will be determined. Covalent phosphoenzyme intermediates will be isolated and the structures of enzyme active site peptides will be determined. The stereochemistry of the transfer reaction of optically active phosphorothioate esters will be studied. Covalent modification reactions by alkylating agents including phosphate derivatives of nitrogen mustards will be studied. 31P-NMR will be used to follow the phosphate oxygen-water exchange reaction catalyzed by acid phosphatases. A new phenomenon, an 18O isotope shift on 13C-NMR spectra, will be used to determine the rates of some biochemically important oxygen exchange reactions occurring at carbon.